This application is based on and claims priority to Japanese Patent Application No. 11-310796, filed Nov. 1, 1999, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to fuel injection controls for internal combustion engines used in marine applications. More specifically, the present invention relates to such systems in which fuel injection amounts are adjusted based on an operative position of an associated transmission as well as a throttle position.
2. Related Art
Outboard motors are used to power boats and other watercraft. Outboard motors typically include an internal combustion engine that is surrounded by a protective cowling. The engine of the outboard motor is coupled though a driveshaft to a propulsion device, such as, for example, a propeller. The propulsion device typically lies in the body of water in which the watercraft floats and drives the watercraft in a forward or reverse direction.
The outboard motor typically includes an intake system for supplying air to the engine. The intake system typically includes a throttle control valve, which controls the amount of air flowing through the induction system and into the engine. When the throttle valve is closed, the air flow rate is minimized and when the throttle valve is opened, the flow rate through the induction system can be controlled. The throttle valve usually is coupled to a throttle valve actuator, which is controlled by an operator of the watercraft.
Outboard motors typically also include a fuel injection system for supplying fuel to the engine. Fuel injection systems often include fuel injectors that either inject fuel directly into an air induction device or into a combustion chamber of the engine. The amount of fuel injected through the fuel injectors is determined by a control system, which usually includes an electronic control unit (ECU). Typically, the ECU determines the amount of fuel to be injected through the fuel injectors based upon various engine and ambient conditions, such as, for example, the position of the throttle valve.
Due to the environment in which outboard motors operate, there are some operating conditions that are unique to outboard motors. For example, when the operator releases the throttle valve actuator, the throttle valve rapidly closes (i.e., the throttle valve closes under the biasing force of a spring, as the opening force provided by the operator controlled actuator is removed). In engines used in land vehicles, this causes the engine speed to decrease rapidly. However, in an outboard motor that is attached to a moving watercraft, when the transmission is in forward or reverse, the advancing force of the watercraft tends to drive the propeller, which, in turn, drives the engine. That is, the water surrounding the propeller rotates the propeller, which, in turn, rotates the crankshaft. The engine speed, therefore, does not decrease rapidly. This can cause several problems. For example, because the engine speed does not decrease rapidly, the watercraft is undesirably unresponsive to changes in operator demand. Moreover, excess fuel can pass into the exhaust system which can cause backfiring.
Accordingly, an arrangement of the outboard motor is desired in which the performance of the outboard motor when the throttle valve rapidly closes is improved. Thus, a fuel injection control system is provided in which the amount of fuel injected through the fuel injectors is substantially reduced when the throttle valve rapidly closes and the engine is in forward or reverse drive. However, when the engine is disengaged or in neutral, the fuel injection system is arranged such that the amount of fuel is reduced to a lesser degree as compared to when the engine is in forward or reverse drive.
Accordingly, one aspect of the present invention involves an engine for a watercraft. The engine comprises a cylinder body, at least one cylinder bore being formed in said cylinder body, and a piston being mounted for reciprocation within the cylinder bore. A cylinder head is disposed over a first end of the cylinder bore. A crankcase member is disposed over a second end of the cylinder bore. An output shaft is disposed at least partially within a crankcase chamber that is at least partially defined by the crankcase member. The output shaft powers an output device through a shiftable transmission. A transmission sensor is capable of detecting whether the output device is engaged or disengaged with the output shaft. A combustion chamber is defined at least partially within the cylinder bore between the cylinder head and the piston. An intake conduit communicates with the combustion chamber. A throttle valve is disposed within the intake conduit. The engine further including a throttle valve sensor that is capable of sensing a position of said throttle valve. A fuel injection system includes a fuel injector that supplies fuel to the combustion chamber. The fuel injector includes an actuator to regulate an amount fuel that is injected by the fuel injector. A controller electrically communicates with the actuator for the fuel injector, the transmission sensor and the throttle valve sensor. The controller is adapted to substantially reduce the amount of fuel injected by the fuel injector to a second amount of fuel when the throttle valve is rapidly closed and the output device is engaged.
Another aspect of the present invention involves an engine for a watercraft. The engine comprises a cylinder body, at least one cylinder bore being formed in said cylinder body, and a piston being mounted for reciprocation within the cylinder bore. A cylinder head is disposed over a first end of the cylinder bore. A crankcase member is disposed over a second end of the cylinder bore. An output shaft is disposed at least partially within a crankcase chamber that is at least partially defined by the crankcase member. The output shaft powers an output device through a shiftable transmission. A transmission sensor is capable of detecting whether the output device is engaged or disengaged with the output shaft. A combustion chamber is defined at least partially within the cylinder bore between the cylinder head and the piston. An intake conduit communicates with the combustion chamber. A throttle valve is disposed within the intake conduit. The engine further including a throttle valve sensor that is capable of sensing a position of said throttle valve. A fuel injection system includes a fuel injector that supplies fuel to the combustion chamber. The fuel injector includes an actuator to regulate an amount fuel that is injected by the fuel injector. A controller electrically communicates with the actuator for the fuel injector, the transmission sensor and the throttle valve sensor. The controller is adapted to reduce the amount of fuel injected by the fuel injector to a first amount when the throttle valve is rapidly closed and the output device is engaged and to reduce the amount of fuel injected by the fuel injector to a second amount when the output device is disengaged.
Yet another aspect of the present invention involves a method of controlling an amount of fuel injected into an engine when a throttle valve is rapidly closed. The method comprises detecting a throttle valve angle, determining if the valve is substantially closed and determining whether a transmission of the engine is engaged or disengaged. The method further comprises sensing the engine speed and comparing the engine speed to a first specified value, reducing an amount of fuel injected into the engine by a first amount if the engine speed is greater than the second specified value and the transmission is engaged, reducing the amount of fuel injected into the engine by a second amount if the transmission is disengaged.
A further aspect of the present invention involves a method of controlling an amount of fuel injected into an engine when a throttle valve is rapidly closed. The method comprises, detecting a throttle valve angle, determining if a transmission of the engine is in a first condition or a second condition, and sensing an engine speed.